<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div style="width:100%;
    flex-wrap:wrap;
    align-items: center;
    position: fixed;
    bottom: 15px;">
    <div>
      <button class="button" onclick="switchPreviousQuestion">上一题</button>
      <button class="button" onclick="switchNextQuestion">下一题</button>
    </div>
    <div>
      <button class="submit" onclick="showDialog">提交</button>
    </div>
  </div>
</body>
</html>